Electroflocculation cells have been described in the prior art (see for example German Patent DE 3,641,365 to Klose, U.S. Pat. No. 6,179,991 to Norris, U.S. Pat. No. 6,663,766 to Adin, European Patent EP 6682 44 to Batt; and PCT International Application PCT/WO. 95/15295 to Beaujean).
The publication by Matteson, Michael J., Dobson, Regina L. et al “Electrocoagulation and separation of aqueous suspensions of ultrafine particles”, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 104; 1 (November): 101-109 (1995), and the publication by Vik, E A, Carlson, D A, Eikun, A S and Gjessing, E T, “Electrocoagulation of potable water”, Water Research, 18; 11: 1355-1360 (1984) describe electroflocculation cells or electroflocculation systems.
A disadvantage of the prior art electroflocculation cells is tendency to foul. Solutes present in many ambient waters, such as Calcium Sulfate or Calcium Carbonate or other solutes, are present at or near saturation. Such solutes have a tendency to form scales and foul the equipment. Commonly present suspended hydrocarbons, turbidity, colloids, and particles may also form strongly adherend deposits and oil films on the cell electrodes, thereby causing local pitting resulting in low current efficiency.
Klose, German Patent DE 3641 365 describes an apparatus in which electroflocculation takes place by serpention flow of contaminated water through a bed of vertical positioned electrodes of alternating iron and aluminium sheet metal. Practical examination shows that this configuration has a low volume capacitiy and shows a strong tendency to form nonconducting deposits on the electrodes resulting in low current efficiency.
A similar apparatus in form of a stack of horizontal electrodes made of perforated iron and aluminium metal sheet has been submitted by Adin, U.S. Pat. No. 6,663,766. This electroflocculation cell has local stagnant areas prone to fouling and requires costly machining of the electrode stack.
A vertical and parallel array of aluminium and/or iron electrodes plus a stream of compressed air alongside these electrodes has been proposed by Beaujean PCT/WO. 95/15295. This stream of compressed diminishes fouling of the apparatus, however examination in practice reveals that the current efficiency of this design is poor.
A high volume column type electroflocculation cell has been disclosed by Batt European Patent EP 6682 44. This design however requires one of the electrodes to be of the composite type, something that turns out to be more costly than the use simple electrodes. Moreover, composite electrodes tend to be unstable due to the different dissolution rates of aluminium and iron.
Norris, U.S. Pat. No. 6,179,991 proposes a machine for treating contaminated water comprising a chamber with at least two electrodes having voltages of different polarities and made of multivalent metals and one or more scraper blades in substantial contact with said electrodes wherein said blades are capable of movement along the length of said electrodes to remove accumulated debris. Despite that the problem has been correctly recognized no practical realization is possible because the electrodes thin out. Since an additional cleaning mechanism is necessary this proposal becomes very costly.
There is therefore a significant and unfulfilled need for a new and improved flow-through electroflocculation apparatus, method and system. Such an electroflocculation cell would be resistant to fouling and have high current efficiency. It would furthermore be desirable for such an electroflocculation cell to be easy to manufacture, and not require any unnecessary parts that increase cost, or limit the usefulness of the electroflocculation cell.